Project Summary/Abstract Context Newborn screening (NBS) is a public health service to identify infants who will benefit from early intervention to reduce death, mental retardation and other significant health problems. Preliminary data suggest that Severe Combined Immune Deficiency (SCID) can be identified and effectively treated within the newborn period. Objective To develop, validate and implement SCID NBS tests and algorithm(s) for identifying infants with SCID and to make the assay/algorithm(s) available to public health NBS laboratories for implementation of SCID NBS Design, Setting, and Participants A Massachusetts-wide pilot SCID NBS program encompassing universal offering of optional laboratory screening, reporting and follow-up. The initial laboratory-screening algorithm will be integrated into existing Massachusetts (MA) NBS and will comprise a multiplexed assay for T cell recombination excision circles (TRECs) developed by the New England Newborn Screening Program. Evaluation and validation of assays for other markers of SCID will proceed with expectation for a multi-tiered or combinatorial screening algorithm. Enhancements include expansion of the population screened and of states with technical staff trained in SCID NBS. Intervention Infants identified with a positive NBS will be referred for diagnostic evaluation and those with confirmed diagnoses will be treated and followed in accordance with standard of care and consensus guidelines to be developed by the MA SCID NBS Workgroup. Main Outcome Measures Data to be collected include numbers and outcomes of infants with both negative and positive screens. Results Feasibility, sensitivity and specificity of testing all infants for the absence of TRECs as well as clinical validity, sensitivity and specificity of Luminex bead assays for detection of infants with SCID and best-practice algorithms for implementation of SCID NBS. Conclusions Population surveillance of screened infants and outcome evaluations of treated infants will provide data on technical feasibility, clinical validity/utility, SCID incidence and effectiveness of the screening program PUBLIC HEALTH RELEVANCE: NARRATIVE Newborn screening (NBS) is a public health service designed to provide universal early opportunity for identification of infants who have particular medical conditions and who are likely to benefit from early intervention to reduce death, mental retardation and other significant health problems. Severe Combined Immune Deficiency (SCID) holds promise as an ideal condition for identification by population-based NBS if a reasonable test can be demonstrated. The proposed work will demonstrate feasibility of SCID NBS with optimized NBS tests for SCID and generate data from a Massachusetts-wide pilot program to determine whether SCID NBS meets criteria for inclusion on NBS panels.